Union Square was built and dedicated by San Francisco's first American mayor John Geary in 1850 and is so named for the pro-Union rallies that happened there before and during the United States Civil War. Since then, the plaza underwent many notable changes with the most significant first happening in 1903 with the dedication of a 97 ft (30 m) tall monument to Admiral George Dewey's victory at the Battle of Manila Bay during the Spanish American War. It also commemorates U.S. President William McKinley, who had been recently assassinated. The figurine at the top of the monument, "Victory", was modeled from the likeness of a local heiress, Alma de Bretteville Spreckels. The second major significant change happened between 1939-1941 when a large underground parking garage was built under the square that relocated the plaza's lawns, shrubs and the Dewey monument to the garage "roof." It was the world's first underground parking garage and was designed by Timothy Pflueger.
During the late 1970s, and through the 1980s and 1990s, the area became a bit derelict as the homeless began to camp in the space. San Francisco's rowdy New Year's parties used to happen yearly at the plaza with some sort of civil disruption and rioting happening afterward. In early 1998, city planners began plans to renovate the plaza to create more paved surfaces for easier maintenance, with outdoor cafes, and more levels to the underground garage. Finally in late 2000, the park was partially closed down to renovate the park and the parking garage.
Today, Union Square retains its role as the ceremonial "heart" of San Francisco, serving as the site of many public concerts & events, art shows, impromptu protests, private parties and events, and the annual Christmas tree and Menorah lighting. Public views of the square can be seen from surrounding high places as the Sir Francis Drake Hotel, Macy's top floor, and the Grand Hyatt hotel.